I have been there & actually I still go through those feelings of no strength. The best thing you can do is surround yourself with people in the Lord, pray for others, and when you feel like you don't know what to do read the bible, pray, and ask God to help you & give you the strength & wisdom to uplift you. Never worry as hard as that may seem give all your trouble to God he will work them out. "God does not always answer when you call but he is always on time." 

What is going on at home? Are you living with parents or on your own? At times when I feel really restless, day or night, I can get out and pray, open my Bible and read about the lives of some of the people there. It can be a great help. Satan is pretty good at distracting us from doing what we want to do, and especially from God. The closer we get to God the more satan will pull and tug at us.
Father, God, I come to you this morning and ask that you would strengthen the faith and comittment of this one. Father, satans pull can be strong but you are stronger than satan. Father renew this childs faith and increase the joy in their heart as they draw ever closer to you. Lord, grant the courage needed for this one to recomit to you and follow the way you have chosen for them. Bless this life and all they do in Jesus name. AMEN 

Dear Lord,

Please be with this child of yours. Guide them and let them feel yout awesome love and strength so that they may feel revived in their faith. Dear God thank you for all you have done and all you will do in this persons life.

In Jesus name, Amen